Disinfecting use of quaternary ammonium carbonates

ABSTRACT

A method for disinfecting a substrate is provided. The substrate is contacted with a biocidal effective amount of a composition of (a) at least one quaternary ammonium carbonate, bicarbonate, or any combination thereof; (b) a solvent selected from the group consisting of water and propylene glycol; and (c) optionally, a surfactant.

This application is a continuation of Ser. No. 08/931,184, filed on Sep.16, 1997, now U.S. Pat. No. 6,080,789, which is a continuation of Ser.No. 08/352,899, filed on Dec. 9, 1994, now abandoned.

FIELD OF THE INVENTION

This invention relates to the use of quaternary ammonium carbonatecompositions as low corrosion disinfectants, particularly in hard watersolvents.

BACKGROUND OF THE INVENTION

The biocidal activities of other quaternary ammonium compositions havebeen reported. The biocidal activities of various quaternary ammoniumchlorides against bacteria, fungi, and algae are tabulated in CationicSurfactants, E. Jungerman Ed., pp. 56-57, Marcel Dekker, Inc., 1969.Nicholas, “Interaction of Preservatives with Wood,” Chemistry of SolidWood, Advance in Chemistry Series #207, Powell ed., (A.C.S. 1984) notesthat didecyldimethyl ammonium compounds, and particularlydidecyldimethylammonium chloride, are potential biocides. Preston,J.A.O.C.S. 60:567 (1983) concurs and suggests that maximum fungitoxicityis exhibited with dialkyldimethyl compounds having C₁₀-C₁₂ alkyl groups.Butcher et al., Chem Abstracts No. 91:152627b, suggests that thepresence of an acid or a base can affect the activity ofdidecyldimethylammonium quats.

Ruseggan, in U.K. Patent Publication No. 650,304, discloses a detergentwhich includes a tetra alkyl quaternary ammonium halide or hydroxide inwhich two alkyl groups contain from 6 to 9 carbon atoms in eachhydrocarbon group and the other two alkyl groups contain 3 to 9 carbonatoms each together with a weak alkali. Such compositions may alsoinclude an alkali substrate (See U.K. Patent Publication No. 669,506).

Hunter et al., U.S. Pat. No. 3,169,983, disclose glycol monoborate saltsof quaternary amines that are useful as active biocides and fungicidesin soaps, detergents, and dry cleaning compositions.

It has now been discovered that quaternary ammonium carbonates can beused as disinfectants, particularly in hard water. These compositionshave low corrosion properties.

Some carbonate quats can be prepared by heating trimethylamine withcarbon dioxide and methanol above 200° C. and at 85 to 95 atmospheres.Industrial Organic Nitrogen Compounds, Astle Ed. p 66, Reinhold Inc,1961. However, this reaction is limited to the methyl compound becausehigher homologs decompose to olefins by the Hoffman eliminationreaction. See, Organic Reactions, 11, Chptr. 5, 377, Krieger PublishingCo., 1975.

Chem Abst. 110, 212114 (1989) suggests that dimethyl carbonate willreact with triethylamine in methanol in twelve hours at 115° C. andunder pressure to yield a methyl carbonate quat ester.

Chem Abst. 114, 24824 (1991) discloses that 6-hydroxyhexyldimethylaminereacts with dimethyl carbonate to yield a carbonate ester quat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic illustration of the sanitizing effect of acomposition according to the present invention.

FIG. 2 is a graphic illustration of the sanitizing effect of acomposition according to the present invention.

SUMMARY OF THE INVENTION

A method for disinfecting a substrate is provided. The substrate iscontacted with a biocidal effective amount of a composition comprising(a) at least one quaternary ammonium carbonate, bicarbonate, orcombination thereof; (b) a solvent selected from the group consisting ofwater and propylene glycol; and (c) optionally, a surfactant.

DETAILED DESCRIPTION OF THE INVENTION

Quaternary ammonium compounds useful in the present invention arequaternary ammonium compounds having carbonate and/or bicarbonateanions. Preferred quaternary ammonium carbonates have the formula

wherein R¹ is a C₁-C₂₀ alkyl or aryl-substituted alkyl group, or abenzyl group and R² is a C₄-C₁₂ alkyl or aryl-substituted alkyl group,or a benzyl group.

A preferred carbonate quat is one in which R¹ is a C₁-C₂₀ alkyl oraryl-substituted alkyl group and R² is a C₈-C₂₀ alkyl group. Preferably,R¹ and R² are the same C₈-C₂₀ alkyl group. A most preferred carbonatequat is didecyldimethylammonium carbonate wherein R¹ and R² are a C₁₀alkyl group and most preferably an n—C₁₀ alkyl group.Didecyldimethylammonium carbonate, when observed as a 70-80 percent byweight solution in a 50 percent by weight alcohol/50 percent by weightsolvent is a yellow/orange liquid that has a slightly fruity odor. Thisformulation has a flash point of about 160° F., and it reacts withcarboxyl containing compounds.

The stability, and particularly the thermal stability, of carbonatequats is far superior to that of hydroxy quats, making these carbonatequats suitable for concentrating and as stock intermediates for furtherprocessing.

One or more of these carbonate quats can be used alone or in combinationwith the corresponding bicarbonate quat(s). One or more bicarbonatequats can be used alone as well.

Preferred bicarbonate quats have the formula

wherein R¹ and R² are as defined above.

Although certain carbonate quats can be prepared by a variety ofmethods, an indirect synthesis method that can be used to prepare avariety of quaternary ammonium carbonate compositions, including, butnot limited to, quaternary ammonium carbonate compounds, preferablyC₁-C₂₀ alkyl or aryl-substituted alkyl, C₈-C₂₀ alkyl quaternary ammoniumcarbonate compounds including, but not limited to, di C₈-C₁₂ alkylquaternary ammonium carbonate compounds, and most preferablydidecyldimethylammonium carbonate, is preferred.

wherein R¹ and R² are as defined above; preferably R¹ is a C₁-C₂₀ alkylor aryl-substituted alkyl group; R² is a C₈-C₂₀ alkyl group; and mostpreferably R¹ is the same as R² and R¹ is a C₈-C₁₂ alkyl group; R³ is astraight chain C₁-C₄ alkyl group; M is a mono-, bi-, tri-valent metal,preferably a mono-valent metal, and most preferably an alkali metal; andm is 1 if M is mono-valent, 2 if M is di-valent, and 3 if M istri-valent.

An appropriate quaternary ammonium chloride with correspondingsubstituents on the nitrogen atom such as, for example C₁-C₂₀ alkyl oraryl-substituted alkyl, C₈-C₂₀ alkyl, and preferably a di C₈-C₁₂ alkyl,quaternary ammonium chloride is used as a starting material and isreacted with a metal hydroxide to yield a corresponding quaternaryammonium hydroxide intermediate such as, for example C₁-C₂₀ alkyl oraryl-substituted alkyl, C₈-C₂₀ alkyl, and preferably a di C₈-C₁₂ alkyl,quaternary ammonium hydroxide intermediate. The hydroxy quatintermediate(s) and any excess metal hydroxide are then reacted withcarbon dioxide to yield the carbonate quat(s) and the metal carbonate.

Many quaternary ammonium chlorides such as, for example di C₁-C₁₂ alkylquaternary ammonium chlorides, are suitable reactants to prepare theintermediate hydroxy quat, but didecyldimethylammonium chloride ispreferred. The selections of the R¹ and R² substituents of the chloridequat reactant are determinative of the hydroxy quat intermediate, andtherefore, of the carbonate quat product.

Special mention is also made of processes wherein R¹ is a methyl, C₈alkyl, C₉ isoalkyl, C₁₀ alkyl, C₁₂ alkyl, C₁₄ alkyl, C₁₆ alkyl, orbenzyl group; and R² is a C₁₀ alkyl, C₁₂ alkyl, C₁₄ alkyl, or C₁₆ alkylgroup.

The metal hydroxide reactant is a mono-, bi-, or tri-valent metalhydroxide, preferably a mono-valent metal hydroxide, and most preferablyan alkali metal hydroxide such as sodium hydroxide or potassiumhydroxide. Special mention is made of potassium hydroxide. The metalchloride first step reaction product will precipitate and is easilyremoved, i.e. by filtration or the like, yielding a hydroxy quat/solventreaction product. The hydroxy quat can be separated therefrom by dryingor the like, if desired.

The first reaction (III) is conducted in a solvent which comprises aC₁-C₄ normal alcohol. Preferably, the solvent is ethanol, and mostpreferably, anhydrous ethanol. The reaction to form the hydroxy quat istypically an equilibrium reaction, but the use of a C₁-C₄ normal alcoholsolvent drives the reaction sharply to the hydroxy quat.

The amount of metal hydroxide reactant typically is a stoichiometricamount with respect to the quaternary ammonium chloride reactant.Therefore, on a theoretical basis and if the reaction were complete andunequilibrated, there would be no excess of metal hydroxide reactantupon completion of the intermediate reaction. In practice, yield whenusing a stoichiometric amount of metal hydroxide reactant will rangefrom about 65% to about 95%, but will vary, dependent, in part, upon theparticular metal hydroxide reactant.

Yield of the hydroxy quat can be further improved over conventionalmethods by utilization of a stoichiometric excess of metal hydroxideranging from about 2% to about 20% excess. If an excess of metalhydroxide is used yield will be increased to from about 95% to about99%, again varying as above.

The unreacted metal hydroxide is soluble in the hydroxy quat/solventintermediate.

Hydroxy quat and any unreacted metal hydroxide are then reacted with atleast a stoichiometric equivalent of carbon dioxide to yield thequaternary ammonium-carbonate(s), and if any unreacted metal hydroxidewere present, the metal carbonate(s). The conversion of the metalhydroxide to the metal carbonate is the preferred reaction of the twocarbonations and will proceed more rapidly. The metal carbonate willprecipitate and can be separated easily, i.e. by filtration or the like,leaving the stable carbonate quat(s) or carbonate quat(s)/solventreaction product.

The carbonation step can also produce the bicarbonate quat or the metalcarbonate quat as byproducts. The carbonate quat alone or in combinationwith the bicarbonate quat is suitable for use in disinfectantcompositions of the present invention.

Mixing, adding, and reacting of the components in the present inventioncan be accomplished by conventional means known to those of ordinaryskill in the art. The order of addition of reactants or solvent in anyindividual step does not affect the process. Reactants and/or solventcan be added sequentially or simultaneously in any suitable reactionvessel. For example, the metal hydroxide may be dissolved in alcohol andthe resultant mixture added to the chloride quat or the chloride quatmay be dissolved in alcohol and the metal hydroxide added to theresultant mixture. Importantly, the method of the present invention issuitable for commercial scale production techniques and equipment, yetconvenient for small scale work.

Typically, the reactants and solvent of the chloride quat to hydroxyquat reaction (III) will be stirred and heated to from about 20° C. toabout 70° C. and held at that temperature for a period of from about 1hour to about 5 hours. The reaction mixture is then cooled, first toroom temperature and then to about 0° C. where it is held for about 1hour to about 2 hours. Any precipitated metal chloride is collected asis known in the art, i.e. such as by filtration.

Alternatively, the first reaction reactants and solvent can be stirredat a slightly elevated temperature, i.e. from about 20° C. to about 40°C., to yield the hydroxy quat/solvent mixture. Hydroxy quat can beseparated as above.

The carbon dioxide is generally bubbled for a suitable period known tothose of ordinary skill in the art through the hydroxy quat/solventsupernatant after the metal chloride precipitate has been separated.Alternatively, the carbon dioxide can be added as solid dry ice directlyto the hydroxy quat. Typically, this time varies from about 0.5 hour toabout 1 hour at ambient temperature. Any precipitated metal carbonate iscollected as is known in the art, i.e. such as by filtration.

Suitable solvents include water, propylene glycol, or a combinationthereof. Carbonate quats display good tolerance to hard water comparedwith other quats.

Optionally, a surfactant may be added as well. Suitable surfactantsinclude, but are not limited to, non-ionic surfactants, for example,amine oxides, linear alcohol ethoxylate, secondary alcohol ethoxylates,ethoxylate esters, Henkels EPG, betamines, and alkyl polyglycerides.

Other conventional additives such as builders, colorants, perfumes,fragrances, or cleaners may be added as required for application todifferent substrates.

Suitable substrates include, but are not limited to, hard and softsurfaces, food containers, and skin.

The amount of quaternary ammonium carbonate(s) used to treat a substrateis a biocidal effective amount, i.e. that amount to sanitize ordisinfect the substrate. A biocidal effective amount of at least onequat is mixed with a suitable solvent such as water or propylene glycol.The biocidal effective amount will depend upon the use intended and canbe determined by one of ordinary skill in the art in light of thepresent detailed disclosure.

A substrate is considered disinfected or sanitized when 99.999% of thetargeted microorganism(s) on or in the substrate are killed.

Typically, the disinfectant composition can either be supplied in adilutable concentrated form or in a ready to use form. A typicalconcentrate will comprise from about 19% by weight to about 30% byweight of quat based upon 100% by weight of total composition and atypical ready to use formulation will comprise from about from 10 ppm toabout 10,000 ppm of quat based upon total composition.

Treatment of the substrate is accomplished by any means known to thoseof ordinary skill in the art including, but not limited to, dipping,soaking, brushing, spraying, mopping, washing, or the like. The lengthof treatment required will vary according to treatment conditions, theselection of which are known to those skilled in the art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate the invention without limitation. Allparts and percentages are given by weight unless otherwise indicated.

EXAMPLE 1

Water (86.55%), ethylene diamine tetra acetic acid (EDTA Acid) (Versene100—Dow Chemical Co.) (0.75%), surfactant (Barlox 12—Lonza, Inc.) (5%),and didecyldimethylammonium carbonate (50% active) (7.7%) were mixed toyield a biocidal composition having a pH of 9.85.

A 20 ml aliquot was frozen overnight in a vial and then was completelythawed at ambient temperature. Results are illustrated in Table 1.

Another 20 ml aliquot was heated at 50° C. for 30 days to evaluateaccelerated stability.

Results are illustrated in Table 1.

EXAMPLE 2

Water (84.80%), EDTA Acid (Versene 100) (2.5%), surfactant (Barlox12—Lonza, Inc.) (5%), and didecyldimethylammonium carbonate (7.7%) weremixed to yield a biocidal composition having a pH of 10.1. Freeze/thawstability and accelerated stability were determined according to theprocedures of Example 1.

Results are illustrated in Table 1.

EXAMPLE 3

Water (86.3%), EDTA Acid (Versene 100) (1%), surfactant (CarsononN-9—Lonza, Inc.) (5%), and didecyldimethylammonium carbonate (50%active) 7.7%) were mixed to yield a biocidal composition having a pH of9.63. Freeze/thaw stability and accelerated stability were determinedaccording to the procedure of Example 1.

Results are illustrated in Table 1.

TABLE 1 Stability Example 1 2 3 Freeze/Thaw No separation No separationNo separation Stability No precipitation Precipitation present Noprecipitation No darkening Accelerated No separation No separation Noseparation Stability No precipitation No precipitation No precipitationNo darkening No darkening No darkening

EXAMPLE 4

P. aeruginosa with 5% organic load was dried on stainless steel carriersand then immersed in 600 ppm active of a disinfectant compositionprepared according to the method of Example 1 in 400 ppm hard water.

After 10 minutes contact time to the disinfectant, the carriers areaseptically transferred to 10 ml of letheen broth (neutralizer/growthmedia).

These letheen broth tubes with the carriers are then incubated at 37±1°C. for at least 48 hours. After 48 hours, a cloudy letheen tubeindicates growth or failure and a clear tube indicates no goth or pass.Results are illustrated in Table 2. Carrier counts were performed on 10%of the inoculated carriers. Results are illustrated in Table 2.

EXAMPLE 4A

The method of Example 4 was followed, substitutingdecylisononyldimethylammonium chloride (Bardac 2180—Lonza, Inc.) for thedisinfectant composition.

Results are illustrated in Table 2.

EXAMPLE 5

The method of Example 4 was followed, substituting the disinfectantcomposition prepared according to the method of Example 3.

Results are illustrated in Table 2.

EXAMPLE 6

The method of Example 4 was followed, substituting 600 ppm active ofdidecyldimethylammonium carbonate (DDA-CO₃) for the disinfectantcomposition.

Results are illustrated in Table 2.

EXAMPLE 7

The method of Example 4 was followed, substituting 700 ppm active ofDDA-CO₃ for the disinfectant composition.

Results are illustrated in Table 2.

EXAMPLE 8

The method of Example 4 was followed, substituting 800 ppm active ofDDA-CO₃ for the disinfectant composition.

Results are illustrated in Table 2.

TABLE 2 Disinfecting Example # Positives/Total Carrier Counts (10⁶) 42/60 1.30 4A 1/20 1.14 5 0/60 1.34 6 0/60 5.7 7 0/20 4.6 8 0/20 9.0

EXAMPLE 9

The method of Example 6 was followed substituting S. aureus for P.aeruqinosa.

Results are illustrated in Table 3 below.

TABLE 3 Disinfecting Example # Positives/Total Carrier Counts (10⁶) 90/20 3.6

EXAMPLE 10

A Ross-Miles pipette (ASTM D1173-53 (reapproved 1940)) was filled withDDA-CO₃(1000 ppm active) solution. The solution was run out of thepipette at the top of a clear Ross-Miles receiver. Foam height was readimmediately and after 5 minutes by measuring foam production at the topof the foam column at the highest average height to which the rim of thefoam has reached. This height is proportional to the volume of airremaining in the foam. The average of two runs is illustrated in Table4.

COMPARATIVE EXAMPLE 10A

The method of Example 10 was followed substituting Bardac 2180 for theDDA-CO₃.

Results are illustrated in Table 4.

EXAMPLE 11

The method of Example 10 was followed substituting decylisononyldimethylammonium carbonate for the DDA-CO₃.

Results are illustrated in Table 4.

TABLE 4 Foam Properties - 25° C. Disinfectant Foam Foam Level ExampleLevel (mm) After 5 minutes (mm) 10 136 126 10A 131.5 42.5 11 134.5 75

EXAMPLE 12

19 ml of water containing varying amounts of hard water and containing150 ppm (active) of DDA-CO₃ were inoculated with E. Coli (ATCC #1229).After 30 seconds contact time, 1 ml of the inoculated 99 mls wastransferred to neutralizer blanks. Then 1.0 ml and 0.1 ml of the 30seconds neutralizer blanks were plated on to agar to be incubated at37±1° C. for 48 hours. The plates were then counted to find the numberof surviving organisms after 30 seconds contact time. These numbers werecompared to the initial numbers count to yield the percent reduction.

Results are illustrated in FIG. 1.

COMPARATIVE EXAMPLE 12A

The method of Example 12 was followed, substituting Bardac 2250 for theDDA-CO₃.

Results are illustrated in FIG. 1.

EXAMPLE 13

The method of Example 12 was followed, substituting 100 ppm (active)DDA-CO₃ for the DDA-CO₃.

Results are illustrated in FIG. 2.

COMPARATIVE EXAMPLE 13A

The method of Example 13 was followed, substituting Bardac 2250 for theDDA-CO₃.

Results are illustrated in FIG. 2.

The horizontal axis on FIG. 1 represents the hard water levels (800,1000, 1100, 1200, and 1400 ppm) and the vertical axis represents theaverage number of surviving organisms at 30 seconds contact time. In1400 ppm hard water, the DDA-CO₃ average bacterial survival was 1302.5cfu/plate which is below the highest number of surviving organisms(FIG. 1) that meet the 99.999o kill criteria for the food contactsanitizer test. Bardac 2250 in the same experiment had an averagebacterial survival that was 5 times higher, 6597.5 cfu/plate (FIG. 1),which does not meet the 99.9990% kill criteria.

The results of FIG. 2 show that DDA-CO₃ at 100 ppm active in 800 ppmhard water meets the 99.999% kill criteria for the sanitizer test with575 cfu/plate average bacterial survival. Bardac 2250 at 100 ppm activein 800 ppm hard water has 18482.5 cfu/plate average bacterial survivalwhich does not meet the 99.999% kill criteria. These results illustratethe hard water tolerance of the e compositions of the present invention.

EXAMPLE 14

Metal specimens of carbon and alloy steel and an aluminum alloy w ereexposed to didecyldimethylammonium carbonate (46.2% pure). Observationswere made after 28 and 90 days, and the amount of weight loss of metalwas calculated.

No weight loss w as noted for the aluminum alloy specimens. However,some discoloration was observed and a small portion of the outer surfacewas pitted, possibly due to oxidation.

The carbon and alloy steel specimens did not exhibit any outward signsof interaction with the carbonate quat. The metal surface was bright andshiny, similar to test initiation. There was a slight rate of corrosion,calculated to be 0.0151 and 0.00630 mils per year for the 28 and 90 dayspecimens, respectively. It appeared that the corrosion rate decreasedwith time, as the appearance of the test material from the 28-day andthe 90-day exposures did not change significantly.

All patents, applications, articles, publications, and test methodsmentioned above are hereby incorporated by reference.

Many variations of the present invention will suggest themselves tothose skilled in the art in light of the above detailed description.Such obvious variations are within the full intended scope of theappended claims.

What is claimed is:
 1. A method for disinfecting a steel substrate, saidmethod comprising contacting the substrate with a biocidal effectiveamount of a composition comprising (a) at least one quaternary ammoniumcompound selected from the group consisting of a quaternary ammoniumcarbonate, a quaternary ammonium bicarbonate, and a combination thereof;(b) a solvent selected from the group consisting of propylene glycol,water, and a combination thereof; and (c) optionally a surfactant. 2.The method of claim 1, wherein the quaternary ammonium carbonate has theformula

and the quaternary ammonium bicarbonate has the formula

wherein R¹, R², R³, and R⁴ independently are a C₈-C₁₂ alkyl group. 3.The method of claim 2, wherein R¹, R² ₁ R³, and R⁴ are the same C₈-C₁₂alkyl group.
 4. The method of claim 3, wherein R¹, R² ₁ R³, and R⁴ areC₁₀ alkyl groups.
 5. The method of claim 2, wherein R¹ and R² are thesame and R³ and R⁴ are the same.
 6. The method of claim 1, wherein thesolvent is water.
 7. The method of claim 1, wherein the surfactantcomprises a non-ionic surfactant.
 8. The method of claim 6, wherein saidsurfactant is selected from the group consisting of amine oxides, linearalcohol ethoxylates, secondary alcohol ethoxylates, ethoxylate ethers,betamines, alkyl polyglycerides, and mixtures thereof.
 9. The method ofclaim 8, wherein the surfactant comprises nonyl phenol ethoxylate. 10.The method of claim 1, wherein the composition further comprises (d) abuilder, (e) a colorant, (f) a perfumer, (g) a fragrance, or (h) acombination thereof.
 11. The method of claim 1, wherein the substratecomprises stainless steel.